This invention relates in general to molecular biological systems created with color beads and, more particularly to a means by which a micro-array reader can determine the colors used for encoding random beads.
Ever since it was invented in the early 1990s (Science, 251, 767-773, 1991), high-density arrays formed by spatially addressable synthesis of bioactive probes on a 2-dimensional solid support has greatly enhanced and simplified the process of biological research and development. The key to current micro-array technology is deposition of a bioactive agent at a single spot on a microchip in a xe2x80x9cspatially addressablexe2x80x9d manner.
Current technologies have used various approaches to fabricate micro-arrays. For example, U.S. Pat. No. 5,412,087, issued May 2, 1995, McGall et al., and U.S. Pat. No. 5,489,678, issued Feb. 6, 1996, Fodor et al., demonstrate the use of a photolithographic process for making peptide and DNA micro-arrays. The patent teaches the use of photolabile protecting groups to prepare peptide and DNA micro-arrays through successive cycles of deprotecting a defined spot on a 1 cmxc3x971 cm chip by photolithography, then flooding the entire surface with an activated amino acid or DNA base. Repetition of this process allows construction of a peptide or DNA micro-array with thousands of arbitrarily different peptides or oligonucleotide sequences at different spots on the array. This method is expensive. An inkjet approach is being used by others e.g., U.S. Pat. No. 6,079,283, issued Jun. 27, 2000, Papen et al., U.S. Pat. No. 6,083,762, issued Jul. 4, 2000, Papen et al., and U.S. Pat. No. 6,094,966, issued Aug. 1, 2000, Papen et al., to fabricate spatially addressable arrays, but this technique also suffers from high manufacturing cost in addition to the relatively large spot size of 40 to 100 xcexcm. Because the number of bioactive probes to be placed on a single chip usually runs anywhere from 1000 to 100000 probes, the spatial addressing method is intrinsically expensive regardless how the chip is manufactured. An alternative approach to the spatially addressable method is the concept of using fluorescent dye-incorporated polymeric beads to produce biological multiplexed arrays. U.S. Pat. No. 5,981,180, issued Nov. 9, 1999, Chandler et al., discloses a method of using color coded beads in conjunction with flow cytometry to perform multiplexed biological assay. Micro-spheres conjugated with DNA or monoclonal antibody probes on their surfaces were dyed internally with various ratios of two distinct fluorescence dyes. Hundreds of xe2x80x9cspectrally addressedxe2x80x9d micro-spheres were allowed to react with a biological sample and the xe2x80x9cliquid arrayxe2x80x9d was analyzed by passing a single micro-sphere through a flow cytometry cell to decode sample information. U.S. Pat. No. 6,023,540, issued Feb. 8, 2000, Walt et al., discloses the use of fiber-optic bundles with pre-etched microwells at distal ends to assemble dye loaded micro-spheres. The surface of each spectrally addressed micro-sphere was attached with a unique bioactive agent and thousands of micro-spheres carrying different bioactive probes combined to form xe2x80x9cbeads arrayxe2x80x9d on pre-etched microwells of fiber optical bundles. More recently, a novel optically encoded micro-sphere approach was accomplished by using different sized zinc sulfide-capped cadmium selenide nanocrystals incorporated into micro-spheres (Nature Biotech. 19, 631-635, (2001)). Given the narrow band width demonstrated by these nanocrystals, this approach significantly expands the spectral bar coding capacity in micro-spheres.
Even though the xe2x80x9cspectrally addressed micro-spherexe2x80x9d approach does provide an advantage in terms of its simplicity over the old fashioned xe2x80x9cspatially addressablexe2x80x9d approach in micro-array making, there are still needs in the art to make the manufacture of biological micro-arrays less difficult and less expensive and to simplify the process for identifying the color spectrum used to encode the beads (micro-spheres) used in micro-array receivers.
According to the present invention, there is provided a solution to the problems and fulfillment of the needs discussed above.
According to a feature of the present invention, there is provided an apparatus for calibrating a micro-array receiver comprising;
a micro-array receiver including a substrate having coated a biologically active region with a composition including a first set of micro-spheres modified with a biological probe and containing an optical bar code generated from at least one colorant associated with said micro-spheres; and
a calibration region associated with said substrate, said region being outside said biologically active region and having an area containing said optical bar code color.
The invention has the following advantages.
1. A robust means is provided by which a micro-array reader can identify the color spectrum used to encode micro-spheres (beads) used in random array structures.
2. A calibration color region is provided on the micro-array receiver having identifying marks adjacent thereto to facilitate location of the calibration region by the micro-array reader.